Search results for HNMT

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Species

Types

Compartments

Reaction types

Search properties

Protein (1 results from a total of 1)

Identifier: R-HSA-175994
Species: Homo sapiens
Compartment: cytosol
Primary external reference: UniProt: HNMT: P50135

Reaction (2 results from a total of 2)

Identifier: R-HSA-175993
Species: Homo sapiens
Compartment: cytosol
Histamine (Hist) plays important biological roles in cell-to-cell communication via by binding to histamine receptors and its local action is terminated primarily by methylation. Histamine is inactivated principally by two enzymes: histamine N-methyltransferase (HNMT) and diamine oxidase. HNMT uses the methyl donor AdoMet, methylates Hist to form methylhistamine (MetHist) (Yamauchi et al. 1994). The common polymorphism T105I correlates with high (T) or low (I) activity phenotypes (Horton et al. 2001, Rutherford et al. 2008).
Identifier: R-HSA-2408544
Species: Homo sapiens
Compartment: cytosol
A set of methyltransferases (MetTrans(1)) consisting of the proteins histamine-N-methyltransferase (HNMT), glycine-N-methyltransferase (GNMT), and nicotinamide-N-methyltransferase (NNMT) remove a methyl group from adenosylselenomethionine (AdoSeMet) to leave adenosylselenohomocysteine (AdeSeHCys). This reaction is inferred from the event in rat involving the set of methyltransferases (MetTrans(2)) consisting of the proteins histamine-N-methyltransferase (Hnmt), glycine-N-methyltransferase (Gnmt), and nicotinamide-N-methyltransferase (Nnmt) (Kajander et al. 1991).

Pathway (1 results from a total of 1)

Identifier: R-HSA-156581
Species: Homo sapiens
Methylation is a common but minor pathway of Phase II conjugation compared to glucuronidation or sulfonation. The cofactor used in methylation conjugation is S-adenosylmethionine (SAM). SAM is the second most widely used enzyme substrate after ATP and is involved in a wide range of important biological processes. SAM is sythesized from methionine's reaction with ATP, catalyzed by methionine adenosyltransferase (MAT). There are two genes, MAT1A and MAT2A, which encode for two homologous MAT catalytic subunits, 1 and 2.
During conjugation with nucleophilic substrates, the methyl group attached to the sulfonium ion of SAM is transferred to the substrate forming the conjugate. SAM, having lost the methyl moiety, is converted to S-adenosylhomocysteine (SAH). SAH can be hydrolyzed to form adenosine and homocysteine. Homocysteine can either be converted to glutathione or methylated to form methionine, thus forming the starting point for SAM synthesis and completing the cycle.
Fuctional groups attacked are phenols, catechols, aliphatic and aromatic amines and sulfhydryl-containing groups. The enzymes that catalyze the transfer of the methyl group to these functional groups are the methyltransferases (MT). MTs are small, cytosolic, monomeric enzymes that utilize SAM as a methyl donor. There are many MTs but the best studied ones are named on the basis of their prototypical substrates: COMT (catechol O-methyltransferase), TPMT (thiopurine methyltransferase), TMT (thiol methyltransferase), HNMT (histamine N-methyltransferase) and NNMT (nicotinamide N-methyltransferase). An example of each enzyme mentioned is given. In each case, a typical substrate for the enzyme is shown.
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